Russia warns West Against Iran Strike, Sanctions

And they are right. The language from the U.S. government is reminiscent of that prior to the invasion of Iraq. The difference is that an attack on Iran would lead to retaliation, most likely against Israel. That could easily lead to escalation:

Russia warned on Wednesday that an attack on Iran would cause a catastrophe and said US and European Union sanctions against Tehran were aimed at triggering popular discontent by "strangling" the economy.

Foreign Minister Sergei Lavrov said that Western sanctions against Iran and talk of a potential attack undermine efforts to revive negotiations aimed at ensuring it does not develop nuclear weapons.

[...]"I have no doubt that it would pour fuel on a fire which is already smoldering, the hidden smoldering fire of Sunni-Shi'ite confrontation, and beyond that (cause) a chain reaction - I don't know where it would stop," he said of an attack.

And unfortunately the Russians are no help:

Russia will block any move at the UN Security Council to impose sanctions on Syria or authorise the use of force, its foreign minister has said.

Sergei Lavrov said Russia would not be able to prevent military intervention, but that it would veto any resolution at the Security Council authorising it.

Russia has circulated its own draft resolution critical of both sides in the 10-month uprising in Syria.

Meanwhile, reports say troops have resumed shelling the town of Zabadani.

Overnight, an opposition leader in contact with residents said the army had agreed to a ceasefire with rebels inside Zabadani, which is close to both the capital Damascus and the Lebanese border.

Radwan Ziadeh told the BBC that commanders had been surprised by the strength of local support for the Free Syrian Army and that many soldiers had defected.